1. Field of the Invention
The present invention relates to piezoelectric components, such as surface acoustic wave devices and piezoelectric thin-film filters, used for delay lines and filters and a method for manufacturing the same. In particular, the present invention relates to piezoelectric components packaged in a chip and a method for manufacturing the same.
2. Description of the Related Art
In recent years, a decrease in the size and weight of electronic devices has caused a growing demand for multifunctional electronic components. In this case, piezoelectric components, such as surface acoustic wave filters (hereinafter referred to as SAW filters) used for SAW devices and piezoelectric filters including piezoelectric thin-film resonators, used for communication apparatuses such as portable phones are required to have decreased size and weight.
A piezoelectric filter includes piezoelectric resonators arranged in a ladder configuration or a lattice configuration. Each resonator includes a Si substrate having an opening or a recessed portion, and a vibrating portion provided by sandwiching the upper and lower surfaces of a thin-film portion having at least one layer of piezoelectric thin-film (comprising ZnO or AIN) provided on the opening or the recessed portion by at least a pair of upper and lower electrodes that face each other. Alternatively, the Si substrate may not include an opening or recessed portion, and a space may be provided between the lower electrode and the Si substrate. In this type of piezoelectric filter, thickness longitudinal vibration generated at the vibrating portion is used. Therefore, a space for vibration must be ensured and the vibrating portion must be protected against water and dust.
On the other hand, a SAW filter is provided by arranging interdigital transducers (hereinafter abbreviated as IDTs), each including a pair of comb-like electrodes including a metal such as Al, on a piezoelectric substrate including crystal, LiTaO3, or LiNbO3. In such a SAW filter, a vibrating space for the IDTs and a SAW-propagating portion on the piezoelectric substrate must be ensured, and the IDTs must be protected against water and dust.
In the above-described piezoelectric filter and SAW filter, a die bonding agent is applied to the bottom surface of a package including a ceramic material, such as alumina, elements of the piezoelectric filter or the SAW filter are mounted on the package by die bonding, a terminal in the package is connected to electrodes of the elements by wire bonding, and then the package is sealed with a lid. Alternatively, in the above-described piezoelectric filter and SAW filter, an electrode land is provided on the bottom surface of the package including alumina, elements of the piezoelectric filter or the SAW filter are mounted on the package by flip-chip bonding, and then the package is sealed with a lid so as to achieve miniaturization.
In the above-described configuration, however, even though the elements in the piezoelectric filter or the SAW filter are miniaturized, miniaturization and lower profile of the piezoelectric filter and SAW filter is not achieved unless the package is miniaturized. Also, the cost for compact package is high. Particularly, in the piezoelectric filter, the vibrating portion is provided on the opening or recessed portion of the substrate, and thus, the vibrating portion may be broken by impact caused by dicing of elements, and pick up or die bonding of elements when packaged.
In the following discussion, Patent Document 1 is Japanese Unexamined Patent Application Publication No. 2001-94390, Patent Document 2 is Japanese Unexamined Patent Application Publication No. 11-150441, Patent Document 3 is Japanese Unexamined Patent Application Publication No. 2001-60642, and Patent Document 4 is Japanese Unexamined Patent Application Publication No. 2001-244785.
On the other hand, bumps are used for packaging in Patent Documents 1 to 3. According to these Patent Documents, flip-chip mounting, in which a SAW element is bonded to a base substrate via bumps on the base substrate is used. In this method, space for wire bonding is not required, which results in miniaturization of the SAW filter. However, conductive pads corresponding to the bumps must be provided in the SAW element, which reduces an effective area of the SAW element. As a result, miniaturization of the SAW filter is difficult and the cost of forming the bumps is incurred.
In Patent Document 4, a SAW element is mounted on a base substrate provided with a through hole that faces a lead electrode of the SAW element and a conductive agent is filled in the through hole, so as to form an external circuit connecting portion. In this manner, the SAW filter is miniaturized.
In the configuration described in Patent Document 4, however, since the SAW filter is formed by bonding the base substrate to the SAW element, the thickness of the SAW filter increases due to the base substrate.